It is often the case that you don't have all the components required to build a circuit that is developing in your mind. Or, perhaps the circuit you wish to develop uses dangerously high voltages and currents. In such cases, it makes sense to use a simulator to test the idea in safety. Simulators are now commonly available, with the Tinkercad Circuits platform covered here accessible in your web browser. As well as simulating circuits, it can also execute Arduino code, as we show here.